renal artery stenosis
With renal artery stenosis, ‘stenosis’ means narrowing, which refers to a progressive narrowing of the renal artery, which carries blood to the kidney.This means that the blood downstream of the narrowed spot that goes to the kidney is at lower pressure, which gets sensed by the kidney.Since an important role of the kidney is to sense and help the maintain a normal blood pressure, the kidney then tries to raise blood pressure throughout the body.
肾动脉狭窄，“狭窄”指的变窄，这指的是肾动脉的一种进行性缩窄，它将血液输送到肾脏。这就意味着，流向肾脏的狭窄部位的血液处于较低的压力，这是由肾脏感觉到的。由于肾脏的一个重要作用是感觉和帮助维持正常的血压，肾脏然后试图提高整个身体的血压。
Inside the kidney, there are millions of nephrons, each of which help to filter the blood and then fine-tune the composition of blood by carefully reabsorbing and secreting electrolytes as fluid passes through various parts of the nephron.Blood approaches the nephron via the afferent arteriole.You can remember it as ‘A’ for approach, and then forms a tangle of capillaries called the glomerulus, before exiting via the efferent arteriole - “e” for exit.That efferent arteriole goes on to split into another set of capillaries - the vasa recta- which surround the nephron, and then blood leaves via the venule.
在肾脏内部，有数以百万计的肾单位，每一种都有助于滤过血液，然后通过仔细地吸收和分泌电解质，当血流通过肾单位不同部分时，对血液的成分进行微调。血液通过入球小动脉进入肾单位。你可以把它记作“A”进入，然后形成一团叫肾小球的毛细血管，然后通过出球小动脉“e”离开。出球小动脉继续分裂成另一组毛细血管，即直小血管，它环绕着肾单位，然后血液通过静脉流出。
So there are two capillary beds per nephron, usually we think of it going arteriole - capillary- venule, but in the nephron it goes arteriole - capillary - arteriole - capillary - and finally venule.So nephrons have the general shape of the letter “U”, with the beginning and end portions getting pretty close to each other.The reason that this matters, is that over here, lining the inside of the afferent arteriole are endothelial cells.Wrapped around them are juxtaglomerular cells which are super special smooth muscle cells that contract down like normal smooth muscle cells, but also have the ability to release a hormone called renin in response to low blood pressure.
因此，每个肾单位有两张毛细血管床，通常我们认为它是小动脉-毛细血管-静脉，但在肾单位中它是动脉-毛细血管-动脉-毛细血管-最后是静脉。所以肾单位有字母“U”的一般形状，开头和结尾部分非常接近。这很重要的原因是，在这里，在入球小动脉内壁排列着内皮细胞。包裹在它们周围的是球旁细胞，一种超级特殊的平滑肌细胞，它像正常的平滑肌细胞一样收缩，但同时也有能力释放一种叫做肾素的激素，以应对低血压。
Over here, close to the distal convoluted tubule, there is another special group of cells that line the tubule called macula densa cells which are sodium-chloride-sensing cells that detect the sodium concentration in the tubule.These two clusters of cells work together because if the blood pressure falls, less blood is filtered and less sodium gets into the tubule.This is then detected by the macula densa cells and they send out a local prostaglandin signal that reaches the juxtaglomerular cells and causes them to release renin.In addition the juxtaglomerular cells are able to directly sense low pressure in the afferent arteriole, and also respond to sympathetic nerve fibers to release renin.
在这里，靠近远曲小管，有另一种特殊的细胞群，它们排列在小管中，叫做致密斑细胞，它是氯化钠感知细胞，可以检测小管中的钠浓度。这两组细胞一起工作，因为如果血压下降，血液过滤减少，更少的钠进入小管。这会被致密斑细胞检测到，释放一个局部的前列腺信号，到达球旁细胞并使其释放肾素。此外，球旁细胞能够直接感受到入球小动脉的低压力，并刺激交感神经纤维释放肾素。
Now, renin helps to constrict blood vessels and increases sodium reabsorption in the nephrons,which ultimately causes blood pressure to rise.Normally, as the blood pressure rises, the juxtaglomerular cells are no longer triggered to release renin, so balance is restored.
One cause of renal artery stenosis is atherosclerotic plaque buildup, which is where a mix of fat,calcium, and immune cells form a crusty rim on the inside of the artery.Another cause, though, is renal fibromuscular dysplasia, where fibro- refers to fibrous collagen connective tissue, -muscular refers to smooth muscle in the artery wall, and -dysplasia means abnormal development.
现在，肾素有助于收缩血管，增加肾内钠的吸收，最终导致血压升高。正常情况下，随着血压升高，球旁细胞不再刺激释放肾素，所以平衡恢复。
造成肾动脉狭窄的原因之一是动脉粥样硬化斑块的形成，这是脂肪、钙和免疫细胞在动脉内壁形成硬的边缘的地方。另一个原因是肾肌纤维发育不良，纤维--指的是纤维胶原结缔组织，-肌肉指的是动脉壁的平滑肌，-dysplasia是发育异常。
So, renal fibromuscular dysplasia is when something goes wrong with connective tissue and smooth muscles in the walls of renal artery, resulting in a series of bulges and narrow spots that leaves the artery looking like a “string of beads” instead of a uniform cylinder.Fibromuscular dysplasia classically develops in young women, but the exact underlying cause is still unclear.In both atherosclerosis and renal fibromuscular dysplasia, the renal artery narrows and that causes the blood pressure to stay low in the kidney as well as all the kidney’s nephrons.
因此，肾肌纤维发育不良是指在肾动脉壁的结缔组织和平滑肌出现问题，导致一系列的凸起和狭窄，使动脉看起来像一串“珠子”，而不是单一的圆柱体。纤维肌发育不良在年轻女性中有典型的发展，但确切的潜在病因尚不清楚。在动脉粥样硬化和肾肌纤维发育不良中，肾动脉狭窄，使血压在肾脏和肾的肾单位中保持低水平。
As a result, the juxtaglomerular cells release renin, which might raise the blood pressure in the body and vessels before the stenosis, but the pressure in the kidney and the afferent arterioles stays low, so they just keep releasing renin.So renal artery stenosis creates a vicious cycle of high blood pressure, or hypertension,which puts incredible stress on the blood vessels and can contribute to having a stroke or heart attack.Also, since the affected kidney receives less blood than usual, it eventually starts to atrophy or shrink in size, as the kidney cells die off and get replaced by fibrotic scartissue.If the renal artery stenosis involves only one of the kidneys, then the other kidneycan often pick up the slack.
因此，球旁细胞释放肾素，这可能会在狭窄之前提高身体和血管的血压，但是肾脏和入球小动脉内的压力仍然很低，所以他们会继续释放肾素。因此，肾动脉狭窄会造成高血压或高血压的恶性循环，这将给血管带来极大压力，并可能导致中风或心脏病发作。而且，由于受影响的肾脏接受的血液比平时少，它最终会开始萎缩或缩小，肾脏细胞会死亡，并被纤维化的瘢痕组织取代。如果肾动脉狭窄只涉及到一个肾，那么另一个肾小管会代偿。
But if both kidneys are affected, then it can lead to acute kidney injury or acute renal failure.Symptoms are often a result of the hypertension, which if it becomes severe, it can cause symptoms like headaches and blurry vision.The diagnosis is therefore based on seeing if there’s an underlying cause for hypertension.Physical examination might reveal a bruit - which is a whooshing sound heard with astethoscope over the renal arteries in the abdomen caused by the turbulence of bloodflowing through the stenotic part of the renal artery.Basic screening labs like serum creatinine and a urinalysis can help assess kidney functionas well, and imaging studies like ultrasound, CT, and MRI can visualize the kidney.For example, in this CT scan of the abdomen, the atrophied kidney is a lot smaller than the healthy one on the other side.
但如果两个肾脏都受到影响，就会导致急性肾损伤或急性肾衰。症状往往是高血压的结果，如果它变得严重，它会引起像头痛和视力模糊的症状。因此，诊断是基于是否有高血压的潜在病因。体格检查可能会发现杂音——这是一种耳鸣的声音，听诊于腹部的肾动脉，由血液流经肾动脉狭窄部分的湍流引起。基本的检查实验室，如血清肌酐和尿液分析可以帮助评估肾功能，而像超声、CT和MRI等成像研究可以使肾脏形象化。例如，在腹部的CT扫描中，萎缩的肾脏比另一侧的健康肾小得多。
Ultimately, since the problem is in the renal artery, a renal arteriography can be done to visualize the renal artery with dye, to see if there’s evidence of a blockage.Generally atherosclerosis forms in the beginning portion of the renal artery where it branches from the aorta, whereas fibromuscular dysplasia develops in the middle to far end of the renal artery, nearest to the kidney.Treatment of renal artery stenosis is aimed largely at trying to manage hypertension,through using medications, as well as adopting healthy eating and exercising habits.In addition, a surgical procedure called balloon angioplasty can sometimes be used - and this is where a balloon is used to open up the narrowed portions of the renal artery and,in rare cases, a tiny stent is left behind to keep the artery propped open.
An alternative option is to simply bypass the stenosis with another artery that is grafted into place.Ultimately, if one kidney becomes atrophied and nonfunctional, it also might be necessary to remove it
.All right, as a quick recap.Renal artery stenosis is where the artery that carries blood to the kidney becomes more narrow, which reduces the amount of blood that the kidney receives as well as the blood pressure.The kidney senses the low blood pressure and responds by releasing the hormone renin which increases blood pressure - ultimately causing hypertension.Over time the lack of blood can also cause the affected kidney to atrophy.
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最终，由于问题是在肾动脉，肾动脉造影可以用造影剂观察肾动脉，看看是否有堵塞的证据。一般来说，动脉粥样硬化形成于从主动脉分支的肾动脉的起始部分，而纤维肌发育不良则发生在肾动脉远端的中部，离肾脏最近。
治疗肾动脉狭窄主要是通过使用药物治疗高血压，以及采取健康饮食和锻炼习惯。此外，有时还可以使用一种叫做球囊血管成形术的外科手术，在这种情况下，气球被用来打开肾动脉狭窄的部分，在极少数情况下，会留下一个微小的支架，以保持动脉的畅通。
另一种选择是用另一根被移植的动脉来绕过狭窄。最终，如果一个肾萎缩而非功能性，也可能需要切除它。
好的，快速回顾一下。肾动脉狭窄是指将血液输送到肾脏的动脉变得更加狭窄，从而减少了肾脏接受的血液量和血压。肾脏能感知到低血压，并通过释放肾素，升高血压——最终导致高血压。随着时间的推移，缺乏血液也会导致肾脏萎缩。感谢收看，你可以通过众筹，或者订阅我们的频道，或者在社交媒体上向你的朋友介绍我们，来支持我们。
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